Erosion resistant liner for hot fluid containers



May 3, 1966 L., F. GRINA 3,248,874

EROSION RESISTANT LINER FOR HOT FLUID CONTAINERS Filed Dec. l0, 1965 2 Sheets-Sheet 1 Fig.

INVENTOR LAWRENCE F. GRINA A TTOR/VE Y May 3, 1966 L.. F. GRINA 3,248,874

EROSION RESISTANT LINER FOR HOT FLUID CONTAINERS Filed Dec. lO, 1965 2 Sheets-Sheet 2 Fig /ah INVENTOR. LAWRENCE F. GRI NA United States Patent O 3,248,874 ERGSION RESISTANT LINER FQR HOT FLUID CONTAINERS Lawrence F. Grina, La Vale, Md., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Fiied Dec. 10, 1963, Ser. No. 329,591 Claims. (Cl. 60-35.6)

This invention relates to liners for rocket motors, and more particularly to such a liner which is segmented to better withstand the high temperature environmental conditions.

The demand for improved missile performance to increase impulse and burning time for greater range is achieved primarily through the use of very high performance rocket propellants. The severe environment imposed by the use of very high impulse propellants such as the aluminized type operating in the 1500 p.s.i. pressure range and at temperatures in the order of 7000 F. has created several problem areas, namely, chamber insulation, tailpipe liners and nozzle materials.

The increase in propellant gas temperatures and the addition of reactants in the propellant which yield solid and liquid gas particles in the gas stream have made the ablative materials previously used for rocket tailpipe insulation inadequate. It has been the practice to use an inner refractory liner supported by a tubular ablative insulator between the liner and the metal tailpipe casing to protect the latter because of the excellent heat transfer properties of the refractory material and the high temperatures to which these materials are subjected.

This combination of liner and insulator proved to be unsatisfactory for use with the above mentioned propellants because the insulator was unable structurally to support the liner when the insulator became charred by thev high temperatures. Degradation of the insulator caused the refractory liner to crack and be destroyed. Gasiiication of the insulator binder substances and the tendency for these gases to accumulate at the insulator-liner interface is a contributing factor to the short life of the refractory liner.

The erosion-resistant-liner insulation construction of this invention assures the integrity of the refractory liner at higher temperatures than heretofore possible. This result is achieved by constructing the refractory liner and the insulator, respectively, of a composite of interlocking segments, such as frusto-conical sleeves. The pressure and skin friction forces generated by the main gas stream in the tailpipe maintain a wedging action between the refractory liner segments and the insulator segments, respectively, as well as between adjacent liner and insulator segments. In addition to substantially increased structural integrity, the segmented construction allows the dissipation of any gas accumulation between the insulator and the liner by venting the pressurized gas between the segments into the main gas stream. The segmented linerinsulator construction is not limited to rocket motor tailpipes, as it can be employed in other components of rocket motors such as nozzles, exit cones, and chambers.

An important object of this invention is to provide an erosion-resistant-liner insulation construction for a rocket motor container which can better withstand the blast environment of high performance rockets, and a corollary object is to maintain structural support for the refractory liner despite the partial degradation of the insulator.

Another object is to provide an erosion-resistant-liner insulation construction having a segmented construction capable of venting gases accumulating at the insulatorliner interface.

A further object is to provide such a construction wherein the tubular liner and tubular insulator are each Patented May 3, 1966 ICC constructed to provide a wedging action to take up any slack caused by the degradation of the insulator.

Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein;

FIG. 1 is a partial longitudinal section of a subsonic rocket motor tailpipe constructed according to the teaching of this invention;

FIG. 1a is a perspective View of a liner segment;

FIG. 1b is a perspective view of an insulator segment;

FIG. 2 is a longitudinal section of a rocket motor nozzle exit cone constructed according to the teaching of this invention; and

FIG. 3 is a partial longitudinal sectional view of a tailpipe similar to FIG. 1, modified by the employment of a sacrical coolant ring.

Referring to the drawings where the same reference numeral refers to similar parts throughout the drawing, there is shown in FIG. 1 a partial aft portion of an end burning, solid propellant motor chamber 10 having extended therefrom a tailpipe 12, an integral nozzle 13, and terminating in an exit cone 14. For purposes of the following description each of these components may be called generally a structural container and the invention can be utilized in the construction of any one or all of these types of containers.

The aft end of motor chamber 10 terminates in a reduced adapter boss 16 threaded at 18 to receive one end of tailpipe 12, the other end of the tailpipe adjacent nozzle section 13 terminating in an inwardly directed beveled iiange 20 externally threaded to an exit cone tube 22 by means of a threaded ring 24. Tailpipe 12, chamber 10, and tube 22 may be constructed of a conventional S.A.E. 4130 steel which parts must be shielded from the heat of the hot erosive gas indicated by arrow 25 emitting from the chamber, passing through the tailpipe and out through the nozzle.

Shielding of metal tailpipe 12 is accomplished by an internal insulator liner 26 comprising a composite of molded segments 28 made of asbestos phenolic material having ablative properties. In the preferred embodiment, segments 28 are configured fmsto-conical sleeves so that adjacent segments fit substantially nested one within the other, forming a series of staggered shoulders 30 for a purpose presently to be described. The outer wall of each insulator segment 28 is cylindrical at 31 to lit snugly against the inside wall of the tailpipe container. Insulator segment 28 adjacent the aft end of the tailpipe is restrained by tailpipe liange 20. The first segment 28 at the entrance end of the tailpipe is litted around and supported by entrance section 32 of refractory material and secured therto by a bead 33 of aircraft seam sealing compound. An insulator shell 34 which lines rocket motor chamber 10 and a collar 36 are -also secured together by bead 33 which also blocks exhaust gases from entering the crevice between the juncture of the chamber insulator and the tailpipe assembly. Segments 28 are secured within tailpipe 12 at their annular crevices around their peripheries by a bead 33a ofthe same type seam sealing compound described above which retains them in place and, also, prevents the ablative gases from flowing into the crevices and attacking the tailpipe wall.

Insulator liner 26 supports within the tailpipe in concentric relation a refractory liner 37 through which the extremely hot gas stream passes. Refractory liner 37 is preferably made of high strength graphite (P 5890, a grade designation by the manufacturer, Carbone Corp., Booneton, New Jersey), which has excellent erosionresistant properties. Similar to insulator liner 26, refractory liner 37 is preferably constructed of a composite of sleeve segments 38 of frusto-conical configuration designed to be wedged together in partially nested relation. The inner wall of each refractory liner segment 38 is cylindrical at 39 to form a bore opening to provide the passageway for the very hot corrosive gases from the rocket motor chamber as indicated by arrow 2S.

The serrated refractory liner 37 is arranged in staggered relation within serrated insulator liner 26 so that the broader base portion of each liner segment 38 is seated within a respective shoulder 30 formed by adjacent insulator segments 28. It will be noted that liner segments 38 in the assembled nested position as shown in FIG. l, are so supported by the insulation liner to provide a small clearance 40 between adjacent liner segments extending from the insulator liner to the bore opening which clearance functions as vent openings for the escape of gases as will be later explained.

Not only are insulator segments 28 and refractory liner segments 38 partially nested respectively within each other, the serrated refractory liner 37 is also nested within the insulator liner 26. In other words, as shown in the drawing, each liner segment 38 is partially nested in a longitudinal direction within adjacent liner segments, as well as partially nested transversely with a laterally disposed insulation liner segment 28 forming a shingled assembly.

Nozzle .section 13, being a continuance of the tailpipe, is constructed essentially in the same manner, however, instead of graphite refractory liner segments, the nozzle segments 42 are preferably constructed of pure tungsten to withstand the very high erosion rates in this convergent section. Nozzle segments 42 can be coated with a 0.025" layer of zirconium oxide which serves as a heat barrier. It is important that no step exists at juncture 44 of the last liner segment and the first nozzle segment. As the nozzle is converging and diverging, the nozzle segments are varied in configuration, differing from segments 28 and 38 which are respectively identical.

Mounted within exit cone tube 22 is exit cone 46 configured as a diverging sleeve supported adjacent the nozzle by an insulator sleeve 48. Sleeve 22 terminates in an inwardly directed beveled shoulder 58 which restrains insulator sleeve 48 and exit cone 46 to the tailpipe by means of threaded ring 24. Exit cone 46 can be fabricated of the same refractory material as liner segments 38, namely, high strength graphite; and insulator sleeve 48 can be made of the same ablative material as insulator segments 28, namely asbestos phenolic. Like nozzle segments 42, graphite exit cone 46 can be coated with zirconium oxide 51 providing a heat barrier.

FIG. 2 illustrates a modified exit cone 52 having a segmented assembly similar to tailpipe 12 previously described. In FIG. 2, exit cone tube 54 comprises a composite of metal tubular portions 56 threadedly connected together at 57 to facilitate assembly and disassembly of the liner components supported therein. The internal wall of the aft end of each tubular portion terminates in an inwardly directed beveled shoulder 58. Insulation liner 60 is constructed of a plurality of overlapping insulator sleeves segments 62 of varying wall thickness because of the diverging configuration of the exit cone. Insulator sleeves are arranged to present a complementary wall, the sleeves being retained in position by shoulders 58. Insulator segments 62 are constructed of ablative material, such as asbestos phenolic, similar to insulator segments 28.

A refractory liner 64 is likewise constructed of a plurality of overlapping sleeve segments 66, the outer walls of the liner sleeves conforming with the adjacent walls of the insulator sleeves 62 to provide an interlocked assembly. Refractory segments 66 are retained in position by insulator segments 62, which in turn are retained by shoulders 58. Segments 66 can be coated with a layer 67 of zirconium oxide, similar to exit cone 46. It will be observed that the interlocked assembly of insulator segments and liner segments of FIG. 2 is similar to the telescopic interlocking nested arrangement of these same components in tailpipe 12. The exit cone of FIG. 2 can be used with tailpipe 12 or any other type of tailpipe construction, such as in FIG. 3.

FIG. 3 discloses a modified tailpipe construction which is identical to the construction of FIG. 1 except for the addition of a tapered ring 68 of polyethylene or the like positioned between abutting adjacent ends of each pair of aligned insulator sleeves 28 and refractory liner sleeves 38. Ring 68 serves as a sacrificial coolant in conjunction with the erosion-resistant-liner insulation system of FIG. l. The polyethylene ring gradually absorbs some of the heat from the hot gases and sublimes, the vapor therefrom forming a laminar flow along the inside wall of the refractory liner providing a layer of insulation. Clearance 70 between segments 28 and 38 should be larger than in FIG. l to account for a greater wedging movement due to the dissipation of ring 68.

The segmented erosion-resistant-liner insulation construction reacts in the following manner to withstand higher gas temperature and pressures than heretofore possible with the conventional integral non-segmented construction. The operation will be described with reference to the tailpipe and nozzle construction of FIG. l although the same description applies to the exit cone construction of FIG. 2, the modified tailpipe description of FIG. 3, .a rocket motor chamber, or any container or duct carrying very hot and highly erosive gases.

During motor operation, the refractory liner 36 is subjected to the extremely high t-emperature of the rocket motor exhaust gases. This heat is rapidly transferred through refractory liner 37 to the insulation liner 26 because of .the excellent heat transfer properties of the refractory material. The heat causes ablation of the insulator segments 28 and the generation of gases from the insulator binder substances, which gases are readily dissipated through the vent openings 40 between the refactory liner segments 38 and into the main gas stream. In FIG. 3 the sacrificial coolant ring 68 can provide an additional insulating feature.

As the insulator segments degrade by charring, the structural integrity of the refractory liner is maintained by a wedging action between refractory segments 38 caused by the pressure and skin friction generated by the gas stream. The wedging action forces the refractory cones more tightly together for support within the insulation liner. Thus, large voids in the insulation liner and accumulated gases are eliminated which heretofore caused failure of the refractory liner. Actual tests have, demonstrated that the novel erosion-resistant-liner insulation system of this invention when subjected to a highly aluminized propellant having a flame temperature of 7000 F. and pressures up to 1800 p.s.i. can last a period of 58 seconds, over twice as long an exposure as could be obtained with prior art construction.

Obviously many other modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A rocket motor container through which flows a very high temperature gas comprising:

an outer tubular casing;

an inner tubular liner through which flows the hot an insulation tubular liner composed of material having decomposa-ble characteristics under normal rocket operating conditions, said insulation liner being concentrically disposed between the inner liner for protecting the outer casing from the heat and supporting the inner liner;

said inner liner comprising a plurality of wedgedshaped segments partially nested in succession one within the other;

said insulation liner supporting each wedged-shaped segment to provide a clearance between adjacent segments for the venting of gases created by degradation of the insulation liner; whereby degradation of the supporting insulation liner will lbe compensated by a wedging action between the frusto-conical segments.

2. T-he container of claim 1 wherein the wedged-shaped segments are frusto-conical in configuration.

3. The rocket motor container of claim 1 wherein said outer rtubular container is provided with an inwardly directed tapered shoulder to restrain said liners in position.

4. A rocket motor container through which ows a very high temperature gas comprising:

an outer tubular metal casing;

an inner tubular refractory liner through which ilows `the hot gas;

an insulation tubular liner concentrically disposed between t-he inner liner for protecting the outer casing from the heat and supporting the inner liner;

said insulation liner comprising a plurality of frustoconical sleeve segments constructed of a material which is thermally decomposa'ble under normal rocket operating conditions;

successive sleeves partially seated one within the other to form a plurality of serrated shoulders;

means for confining said insulation segments Within the casing;

said inner tubular liner comprising a plurality of frustoconical sleeve segments constructed of refractory material;

successive refractory liner segments partially seated one within the other to form a plurality of serrated shoulders;

the serrated shoulders of the insulation linerseating and supporting the serrated shoulders of the refractory liner;

said Arefractory segments being supported in slightly spaced relation by said insulation segments to provide a vent opening therebetween whereby degradation of the supporting insulation segments will be compensated by a wedging action between the refractory segments.

5. The container of claim 4 wherein said insulation segments are sealed within the outer casing.

References Cited by the Examiner UNITED STATES PATENTS 3,022,190 2/ 1962 Feldman.

3,048,972 8/ 1962 Barlow 60-35 .6 3,073,111 1/1963 Hasbrouck 60-35.6 3,133,411 5/1964 McCorkle 60-35.6 3,137,998 6/ 1964 Beam 60--3966 X 3,142,960 8/1964 Bluck 60-35.6 3,156,091 11/1964 Kraus 60-39.66 X

MARK NEWMAN, Primary Examiner.

CARLTON R. CROYLE, Examiner. 

1. A ROCKET MOTOR CONTAINER THROUGH WHICH FLOWS A VERY HIGH TEMPERATURE GAS COMPRISING: AN OUTER TUBULAR CASING; AN INNER TUBULAR LINER THROUGH WHICH FLOWS THE HOT GAS; AN INSULATION TUBULAR LINER COMPOSED OF MATERIAL HAVING DECOMPOSABLE CHARACTERISTICS UNDER NORMAL ROCKET OPERATING CONDITIONS, SAID INSULATION LINER BEING CONCENTRICALLY DISPOSED BETWEEN THE INNER LINER FOR PROTECTING THE OUTER CASING FROM THE HEAT AND SUPPORTING THE INNER LINER; SAID INNER LINER COMPRISING A PLURALITY OF WEDGEDSHAPED SEGMENTS PARTIALLY NESTED IN SUCCESSION ONE WITHIN THE OTHER; SAID INSULATION LINER SUPPORTING EACH WEDGED-SHAPED SEGMENT TO PROVIDE A CLEARANCE BETWEEN ADJACENT 